The 79-year-old Blue Mountains man devoted his life to searching for the legendary Lithgow Panther, Yowie, UFOs, Atlantis, sea monsters in the Hawkesbury River, and a mysterious ancient civilisation near Orange.

"Rex was driven, that's for sure ... he was so passionate ... I think he would like to be remembered for the sincerity of his work" wife Heather told the CWD.

Gilroy self-published more than a dozen books across five decades. Coverage by the Sydney Morning Herald, Discovery Channel, SBS, and other outlets propelled him to minor celebrity status in the late 20th century.

Adamant the true history of earth and humanity has been greatly misunderstood by mainstream academia, he argued Australia is the true location of Plato's Atlantis and the country was visited by ancient Egyptians.

Heather Gilroy believes her late husband's research into a mysterious and unknown ancient Central West civilisation he said may have lived near Orange was among his finest work.

"In the backblocks of Orange out on Ophir Road there's very interesting rock formations," she said.

"Yes, they could be just natural but we believe a civilisation called the Uru people were modifying a lot of these and adjusting them to their needs.

"For many years he was finding rock carvings here and the Blue Mountains that were not Aboriginal, but he couldn't work out [what they were].

"He kept finding the same symbol and eventually he was able to work out a translation for these symbols and hieroglyphs.

"We believe that this civilisation arose here in Australia and eventually spread out up through Asia and Europe and then east to America."

The manuscript for an autobiography titled Yowie Man: The Life and Times of Rex Gilroy was completed in the weeks before his death. It is yet to be published.

News of the cryptozoologist's passing triggered an outpouring of tributes from across the world on social media.

Gilroy outlined his philosophy with a dedication in his 2005 book Uru: The Lost Civilisation of Australia:

"This is [for] the open-minded, free-thinking visionary, who does not know the meaning of the word impossible.

"The field-working, rugged adventurer who never stops at the foothills, and always wants to see what lies beyond the next mountain.

"The dedicated individualist who has the courage and fortitude to defend his ideas, regardless of overwhelming opposition ... Those who against all reason, dare to dig deeper than anyone before them."

A funeral service will be held 11.30am, 21 April at the Leura Gardens Memorial Park.

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